Mapping and imaging large terrestrial areas present many challenges. One technical issue presented by color images of terrestrial areas relates to color reproduction of raw images. For example, the atmosphere has an undesired distance-dependent influence that can cause a digital image to appear blue and/or hazy. Or, for another example, the sun has an angle-dependent influence that can cause parts of a digital image of a lame terrestrial area to appear brighter than other parts, even though the brightness of the scene itself is relatively uniform. Techniques have been developed, for dealing with these and other issues surrounding the accurate capture of such images in digital form. In particular, techniques have been developed to handle the challenges of accurately capturing scene content in spite of lame, often non-linear, variations across the image.
Thus, the content of an image of a lame terrestrial area can be accurately captured using a high dynamic range, large format camera, such as a Microsoft UltraCam aerial camera. However, the dynamic range of the captured image is typically higher than that of a visual display device such as a computer monitor or a printer on which the image is to be viewed or reproduced. For example, such cameras might capture the image in a format with a 16-bit dynamic range, while a computer monitor or printer might only have an 8-bit dynamic range. Likewise, it would usually be more practical to store and retrieve such image data in a form with the same dynamic range as the visual display device with which it is to be viewed, rather than the larger dynamic range of the image produced by the camera. This is because the reduced dynamic range image will use less storage space and will not require conversion in order to reproduce the data in a visible form. And if the images are stored on a remote location and accessed through the Internet, reducing image's dynamic range will also reduce the bandwidth and time required to download images stored in the cloud to a local computer for display.
On the other hand, it is necessary that the content of the original 16-bit image be preserved, to the greatest extent possible when converting it to an 8-bit image. Otherwise, content of the image will be lost to those who want to view it on a computer monitor, print it, or otherwise make it visible on a visual display device.